Adding,
removing, and accessing header field parameters

Parameters can be associated with header field parts at the time
of adding the part. There are two variants of RHTTPHeaders::SetFieldL():
the first is described previously. The second variant takes four parameters,
of which two specify the part name/value and two specify the parameter name/value.

To
associate more than one parameter with the part, the function must be invoked
repeatedly. This does not create duplicate parts; rather it locates the part
with the specified value, and then adds additional parameters.

To access parameter values, the header name
and parameter name must be specified. RHTTPHeaders::GetParam() is
used, and has an optional fourth parameter in which the part index can be
provided. If not, the API assumes that the first header part contains the
parameter.

The following code from HTTPEXAMPLECLIENT illustrates
the use of header parameters with the WWW-Authenticate header: